By treating silica fine powder with thionyl with thionyl chloride, the silanols on the surface of silica were replaced with chlorine, and then phenylated on reacting with phenyllithium. Red or yellow pigments with silica as core were prepared by deriving the surface groups to a structure similar to organic colors (Sudan I or Tartrazine) and the characteristics of these pigments were investigated. The pigments produced by this method had colors similar to the corresponding dyestuff or the aqueous solution, and specific gravities almost agreed with the silica used as core. These pigments had very good resistance to water, and the surface groups did not disappear during preparation. Resistance to heat, light, and solvents was measured. -- AATA